This requirement is evident from a database point of view, but a
novelty from a programming language point of view, [Atkinson et al. 83].
Persistence is the ability of the programmer to have her/his data
survive the execution of a process, in order to eventually reuse it in
another process. Persistence should be orthogonal, i.e., each
object, independent of its type, is allowed to become persistent as
such (i.e., without explicit translation). It should also be implicit:
the user should not have to explicitly move or copy data to
make it persistent.